Several metabolic pathways present in Streptococcus mutans have been examined using mutant analysis techniques. Analysis of glucose phosphotransferase system (PTS) negative-mutants revealed that the glucose PTS can also be used to transport mannose, glucosamine and 2-deoxy-D-glucose (2DG). Such mutants are resistant to growth inhibition by 2DE and catabolic repression by glucose. Glucose PTS negative-mutants are still capable of rapid growth on glucose and therefore, possess a second glucose transport system. A new pathway for maltose utilization was identified. Maltose is transported into S. mutans by a phosphotransferase system. Maltose, therefore, does not enter the cell as free maltose but rather as maltose-phosphate.